The invention relates to an internal combustion engine comprising a main combustion chamber and a secondary combustion chamber which is arranged in a cylinder head of the internal combustion engine and is connected via a shot channel to the main combustion chamber.
Compression-ignition internal combustion engines, apart from their main combustion chamber, often also have a secondary combustion chamber, such as, for example, a precombustion chamber or a swirl chamber, arranged in the cylinder head. The ignition of the fuel/air mixture takes place in this secondary combustion chamber, and the hot gas jet resulting in the process passes via a shot channel into the main combustion chamber of the internal combustion engine. In addition, when a precombustion chamber is used as a secondary combustion chamber, a deflecting pin is also arranged in the same, and the secondary combustion chamber, at its end pointing towards the main combustion chamber, has a burner base provided with nozzle openings. Secondary combustion chambers of this type are normally made of a highly heat-resistant material by means of which the high temperatures occurring there can be coped with. Nimonic 80 may be mentioned here as an example of such a material.
A disadvantage of these materials is that they are susceptible to carbonization, that is, carbides develop and the carbon diffuses into the metal and cracks it so that it becomes brittle. Damage can consequently occur at especially stressed points of the secondary combustion chamber. Thus crack formation, for example, appears at the thin webs between the nozzle openings in the burner base. To avoid damage of this type, another material must be used. The use of ceramic materials is conceivable, but they have the disadvantage that they are not ductile enough at room temperature; in other words they cannot be readily processed. Another material is provided by so-called oxide-dispersion superalloys (ODS), which, however, lose their strength at very high temperatures and are also expensive.
In the German journal "Nickel-Berichte", Mar. 1960, No. 3, a nickel-aluminum alloy of NiAl.sub.3, solid solution is described as particularly corrosion-resistant at elevated temperatures, which nickel-aluminum alloy therefore appears as an advantageous material for the components described in the invention. However, the solid solutions concern an Al-alloy having a nickel content of, for example, 3-6% by weight. The atoms occupy static places in the lattice structure during the dispersion hardening. The increase, mentioned in the above "Nickel-Berichte", of the high-temperature stability of cast aluminum alloys here relates to the low high-temperature stability of aluminum in general and can raise this, for example, from 200.degree. C. to 300.degree. C.
The materials described in East German Patent Specification 222,930 are also aluminum alloys of solid solutions having a nickel content of 4-10% by weight, to which the above comments apply accordingly.
The materials described here are thus not suitable for use where particular demands are made on the high-temperature stability.
An object of the invention is therefore to make the especially thermally stressed parts of a secondary combustion chamber of an internal combustion engine from a material which has sufficient high-temperature stability with adequate ductility for processing at room temperature and low manufacturing and processing costs.
This object is achieved according to the invention by providing an arrangement wherein at least one of the parts of the secondary combustion chamber which are acted upon by a hot gas jet are made of the material Ni.sub.3 Al intermetallic phase. The parts of a secondary combustion chamber arranged in the cylinder head of an internal combustion engine, which parts are especially thermally stressed, such as the shot-channel burner base provided with openings and extending to the main combustion chamber as well as the deflecting pin arranged in the secondary combustion chamber, are made of a material of intermetallic phase, such as, for example, Ni.sub.3 Al or NiAl. The burner base is here made as a separate part and is subsequently connected, for example welded, to the secondary combustion chamber.
This material Ni.sub.3 Al intermetallic phase here consists of about 90% by weight of nickel and about 10% by weight of aluminum, which are cast and cooled in such a way that no dispersion takes place, but a compact material having an ordered lattice structure results. In order to obtain adequate ductility at room temperature, small admixtures of other substances, such as, for example, 0.02% boron or 0.3% yttrium, can be added to the material. The comments just made also apply to the material NiAl, whose basic constituents are present in the stoichiometric ratio of 1:1.
Such materials of intermetallic phase have a high-temperature stability in the region of 1000.degree. C., that is, in a region as occurs on highly thermally stressed components of internal combustion engines.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.